1. Field of the Invention
The present invention relates to a self-adhesive polymer matrix composed of a polymer which is gel-forming in water, preferably a polyacrylic acid polymer, water, sea algae extract, and a monohydric or polyhydric alcohol. The matrix may be doped with hydrophilic or else hydrophobic active substances. The choice of active substance or substances is made in accordance with the field of application, which is a function of the particular requirements of the skin.
2. Discussion of Background Information
The skin is exposed to continually changing environmental effects and is also subject over time to a series of changes. For instance, as described below, there are changes in the barrier properties, in skin creasing and elasticity, in pigmentation, examples being age spots or abnormal pigmentations such as melasma and the like, and in particular, as a result of exogenous influences, there are also various inflammatory reactions, reactions of the skin subsequent to exposure to UV radiation, i.e., sunburn, and/or irritation as a result of shaving.
As well as the positive effects of sunlight, such as general well-being, the formation of vitamin D3 and the treatment of acne, there are also negative effects, which must be countered.
The damaging effect of the ultraviolet fraction of solar radiation on the skin is general knowledge. Whereas radiation of a wavelength of less than 290 nm, known as the UVC region, is absorbed by the ozone layer in the earth's atmosphere, radiation in the region between 290 nm and 320 nm, known as the UVB region, causes erythema, simple sunburn or even more or less severe burns on the skin.
Numerous compounds are known for protecting against UVB radiation, and are generally derivatives of 3-benzylidenecamphor, of 4-aminobenzoic acid, of cinnamic acid, of salicylic acid, of benzophenone, and of 2-phenylbenzimidazole.
Approximately 90% of the ultraviolet radiation reaching the Earth is composed of UV-A rays with a wavelength between 320 nm and 400 nm. Whereas the UV-B radiation varies greatly depending on numerous factors, e.g., season, time of day or latitude, the UV-A radiation remains relatively constant day by day, independently of seasonal, time-of-day or geographical factors. At the same time the predominant fraction of UV-A radiation penetrates the living epidermis, whereas about 70% of the UV-B rays are retained by the horny layer.
In order to protect against the rays of the UVA region, therefore, certain derivatives of dibenzoylmethane are used, whose photostability (Int. J. Cosm. Science 10, 53 (1988)) is inadequate.
For a long time it was erroneously assumed that the long wave UV-A radiation only has a negligible biological effect and that, accordingly, it is the UV-B rays that are responsible for the majority of photodamage to the human skin. In the meantime, however, numerous studies have demonstrated that UV-A radiation is far more dangerous than UV-B radiation with regard to the triggering of photodynamic reactions, especially phototoxic reactions, and chronic changes to the skin. Thus it has emerged that UV-A radiation leads to damage to the elastic and collagenic fibers of the connective tissue, causing the skin to age prematurely. Here, elasticity and water storage capacity of the skin are reduced, i.e., the skin becomes less smooth and tends to form wrinkles. This kind of wrinkling is also referred to as light-induced skin aging. The markedly high incidence of skin cancer in places with high insolation shows that, evidently, damage to the inherited information in the cells is also brought about by sunlight. Moreover, the damaging effect of UV-B radiation can be further intensified by UV-A radiation.
Since the contribution of the different wavelength ranges of UV light to light-induced skin aging have not been fully elucidated, it is increasingly assumed nowadays that preventive protection both against UV-A rays and against UV-B rays, through the application, for example, of sunscreen substances to the skin in the form of a cosmetic or dermatological formulation, is of fundamental importance. Cosmetic or dermatological compositions ought, when applied to the skin in a thin layer, to protect it against the adverse consequences of solar radiation.
UV radiation, however, can also, as noted above, lead to photochemical reactions, with the photochemical reaction products then intervening in the skin's metabolism.
Photochemical reaction products of this kind are predominantly free-radical compounds, examples being hydroxyl radicals. Undefined free-radical photo products as well, formed in the skin itself, may manifest uncontrolled secondary reactions, owing to their high reactivity. But singlet oxygen as well, a non-radical excited state of the oxygen molecule, can occur under UV radiation, as can short-lived epoxides and many others. Singlet oxygen, for example, is distinguished from the triplet oxygen that is normally present (free-radical ground state) by its increased reactivity. However, there are also excited, reactive (free-radical) triplet states of the oxygen molecule. Processes of this kind, via oxidative damage to various skin structures, play a very substantial role in light-induced skin aging (including wrinkling).
Furthermore, UV radiation is an ionizing radiation. There is therefore a risk of ionic species forming under UV exposure, these species then having the capacity to intervene, themselves, oxidatively in the biochemical processes.
In order to prevent these reactions, additional antioxidants and/or free-radical scavengers can be incorporated into the cosmetic and/or dermatological formulations.
The use of vitamin E, a substance having a known antioxidative effect in sun protection formulations, has already been proposed, but the effect achieved here also remains a long way behind the hoped-for effect.
It was therefore an object of the invention to provide active cosmetic, dermatological, and pharmaceutical substances in preparations and also sun protection formulations which serve for the prophylaxis and treatment of light-sensitive skin, especially photodermatoses, preferably polymorphic photodermatosis.
Further terms for polymorphic photodermatosis are PLD, PLE, Majorca acne, and a host of further designations, as reported in the literature (e.g., A. Voelckel et al., Zentralblatt Hautund Geschlechtskrankheiten (1989), 156, p. 2).
Antioxidants are used principally as substances for protection from the spoiling of the preparations comprising them. It is nevertheless known that in human and animal skin, as well, unwanted oxidation processes may occur.
The essay “Skin Diseases Associated with Oxidative Injury” in “Oxidative Stress in Dermatology”, p. 323 ff. (Marcel Decker Inc., New York, Basle, Hong Kong, editors: Jürgen Fuchs, Frankfurt, and Lester Packer, Berkeley, Calif.) sets out oxidative damage to the skin and its more precise causes.
For the purpose of preventing such reactions, as well, antioxidants and/or free-radical scavengers may be additionally incorporated into cosmetic or dermatological formulations.
Certain antioxidants and free-radical scavengers are known. Thus it has already been proposed, in U.S. Pat. Nos. 4,144,325 and 4,248,861, and from numerous other documents, to use vitamin E, a substance with a known antioxidative effect, in sun protection formulations; nevertheless, here again, the effect achieved remains a long way behind that hoped for.
It would be advantageous to find ways to avoid the disadvantages of the prior art. In particular it would be desirable that the effect of the elimination of the damage caused by environmental noxae and the prophylaxis are durable, sustained and without the risk of side effects.
Remedying these deficiencies would be desirable.
Sunbathing is perceived by the majority of people as being pleasurable, and the deleterious consequences are not considered to start with. In recent years, however, an awareness has certainly developed of the adverse consequences of excessively intensive solar irradiation, and so the use of more strongly protecting sun protection compositions is on the increase. Sunburn or photoerythema represents the acute manifestations of exposure to light. As well as the effects of UV rays, which have already been described, a secondary reaction of the skin results, further, in reduced production of sebum and in the skin drying out. In order to alleviate and care for light-ravaged skin, therefore, specific active substances can be used, such as, for example                fat restoratives and moisturizers,        inflammation-alleviating and cooling substances,        local-anesthetic substances and/or        disinfectant substances, in order to prevent possible skin infections.        
As described before, after a latency period of from 2 to 3 hours, a reddening of the skin occurs which is strongly demarcated from the unirradiated skin—this reddening being called erythema solare—if the skin is exposed to the sun or an artificial radiation source for too long. The sunburn which has arisen in this way is differentiated as follows                1st degree: erythema (reddening, sensation of warmth) subsides after 2 to 3 days and disappears with a simultaneous increase in pigmentation,        2nd degree: blistering blisters form on the skin with burning and itching, and areas of the epidermis are shed,        3rd degree: cell damage deep-down cell damage occurs, the body reacts with fever, extensive areas of the epidermis are shed.        
The 2nd and 3rd degrees are also referred to as dermatitis solare.
The formation of erythema is dependent on wavelength. The erythema region of UV-B is between 280 nm and 320 nm. The narrower range around 308 nm is stated as a maximum for the erythema activity of sunlight.
The purpose of what are called aftersun products is to cool the skin after sunbathing and to improve its moisture retention capacity, with the imparting of the cooling effect playing a central part. This cooling effect is generally achieved by high quantities of ethanol, which evaporates spontaneously when the formulation is spread over the skin.
A disadvantage of these prior art formulations, however, is that long-term cooling cannot be achieved, since the ethanol evaporates very rapidly and the resultant cooling effect, accordingly, is of only short duration.
The prior art knows further preparations which, when applied to the skin or mucous membranes, are intended to have a moistening and cooling effect. The literature, for example, describes ionic compounds, especially ammonium salts, as cooling agents. Also in widespread use as cooling preparations are isopropanolic gels with added camphor and added menthol, and, very frequently, essential oils, principally camphor and menthol, but also derivatives thereof, e.g., menthyl lactate or menthyl 3-hydroxybutyrate, are incorporated into cooling compositions.
Menthol, camphor and derivatives thereof, and also other essential oils, lower the sensitivity threshold of the neuronal cold receptors and so bring about a sensation of coldness. In many cases, however, at the same time they produce an increase in circulation, which, in contrast, induces a sensation of heat. The use of these substances, particularly on irritated skin, is in any case problematical. Furthermore, many of these compounds have a poor water-solubility. Their use is consequently limited to a few cosmetics and dermatological products.
It would be desirable, therefore, to find cosmetic or dermatological preparations which do not exhibit the disadvantages of the prior art and which provide long-lasting care in particular to light-ravaged skin.
In adolescent men, the growth of beard hair is triggered by the increased formation of male hormones during puberty. Hormonal disorders in women can also lead to a form of beard growth, but its extent generally remains a long way behind that of male beard growth.
Shaving of the face or other parts of the body with hair growth, such as the legs, armpits or genital area, for example, may be motivated by a variety of impulses—of religious or cultural nature, for example; at its most simple, hair growth is unwanted by the person concerned simply on cosmetic grounds.
Shaving is carried out either dry or wet. The development of new mechanical and electrical wet and dry shaving technologies makes it possible nowadays to remove (beard) hair reliably and thoroughly. For wet shaving, chemical auxiliaries—in the form, for example, of shaving gels, shaving soaps or shaving foams—are generally vital. They are needed in order to soften the (beard) hair and so to minimize the application of force required in order to sever them—and hence to minimize the unpleasant pulling on the shaft of the hair. The softening of the (beard) hairs is achieved by absorption of water, which is made possible by the increase in the pH of the hairs. Wet shaving products therefore generally contain soaps or fatty acid salts whose pH is situated in the range 8-10. Products for wet shaving therefore produce a typical skin sensation which arises after application. The skin is dry and rough to the touch. This skin sensation is also referred to within the cosmetics art as “squeaky feeling”, and is extremely unpopular among consumers both male and female.
In the case of dry shaving as well, cosmetic products are frequently advisable in order to produce as close a shave as possible, i.e., to cut off the (beard) hair as close as possible to the skin surface.
The areas of the skin affected by shaving may, however, be not only irritated by the shaving auxiliaries; the mechanical irritation caused by shaving per se constitutes a burden on the skin, and may result in an unpleasant skin sensation, referred to as “shaving burn”.
It would therefore also be desirable to provide cosmetic or dermatological preparations which better alleviate the secondary reactions of the skin to (mechanical) irritation as a result of shaving.
The pigmentation of human skin is produced essentially by the presence of melanin. Melanin and its degradation products, carotene, degree of perfusion, and the condition and thickness of the Stratum corneum and other skin layers cause the appearance of skin shades ranging from virtually white, in the event of reduced filling or absence of the blood vessels, or yellowish via light brown-reddish, bluish to brown of different shades and finally almost black. The individual regions of the skin display different depths of shading as a result of different amounts of melanin.
Natural melanin protects the skin against penetrating UV radiation. The number of melanin granules produced in the melanocytes determines whether the skin is light or dark. In the case of strong pigmentation, as in colored people, for example, but also in pale skinned people after some UV irradiation, melanin is found in the Stratum spinosum and even in the Stratum corneum as well. It attenuates the UV radiation by up to about 90% before the latter reaches the corium.
Responsible for the pigmentation of the skin are the melanocytes, which are found in the bottom-most layer of the epidermis, the Stratum basale, alongside the basal cells, as pigment-forming cells which, depending on skin type, occur either in isolation or else in greater or lesser accumulation. Melanocytes contain, as characteristic cell organelles, melanosomes, in which the melanin is formed. On excitation by UV radiation, among other factors, the formation of melanin is increased. It is transported via the living layers of the epidermis (keratinocytes) ultimately to the horny layer (corneocytes) and induces a more or less pronounced brownish to brown-black skin color. Melanin is formed as the final stage in an oxidative process in which tyrosine, with the assistance of the enzyme tyrosinase, converts via a number of intermediate stages to the brown to brown-black eumelanins, DHICA and DHI melanin, and/or, with the participation of sulfur-containing compounds (cysteine), to the reddish pheomelanin. DHICA and DHI melanin are formed via the common intermediate stages of dopaquinone and dopachrome. The latter is converted, in some cases with participation of further enzymes, either into indole-5,6-quinone-carboxylic acid or into indole-5,6-quinone, from which the two aforementioned eumelanins are formed. Pheomelanin is formed, inter alia, via the intermediates dopaquinone and cysteinyldopa.
Besides various functions of the melanin endogenous to the skin, including “detoxification”/binding of toxic substances/pharmaceuticals, etc., the function of melanin as a natural UV filter to protect against harmful UV rays, and also the antioxidant function of melanin as a protection against reactive oxygen species (oxidative stress), which may arise as a result of solar radiation, among other factors, is very important for the skin, with regard, among other things, to homeostasis, prevention of skin aging, prevention of sunburn, and so on. Hence there should be not only a cosmetic benefit in the sense of enhanced tanning as a result of the increased synthesis of melanin in the skin following topical application of compounds which increase melanogenesis, but also an additional protection as a result of the various protective functions of melanin.
Depending on their sensitivity to light, the following skin types are generally distinguished:    Skin type I never tans, always burns.    Skin type II hardly tans, burns easily.    Skin type III tans averagely well.    Skin type IV tans easily and lastingly, almost never burns.    Skin type V dark, often almost black skin, never burns.
The natural shielding against harmful UV radiation is a tangible advantage of natural skin tanning. For a number of decades now, moreover, a “healthy” skin color has been seen as a sign of sporting activity, in particular, and is therefore regarded by a broad stratum of consumers to be desirable. Representatives of skin types I and II who wish to enjoy such skin shading are therefore driven in any case to rely on self-tanning products. However, representatives of skin type III as well, who wish not to be exposed excessively to the risks of sunbathing but nevertheless want to appear tanned, are appreciative target groups for self-tanning preparations.
The easiest way of giving one's skin a brown shade is to apply appropriately colored make-up products. Naturally, however, the only parts of the body colored are those covered by the colored products. With the aid of make-up products which can be removed by washing it is possible to achieve a slight skin coloring: for example, extracts of fresh green walnut shells, and henna. One disadvantage of the make-ups is therefore the time-consuming process of their application. A further disadvantage is that they strongly stain textiles such as shirt collars or blouses. Furthermore, the various dyes may have different allergenic potential and may even have an irritant effect on the skin.
Artificial skin tanning can be brought about by cosmetic or medicinal means, with the following approaches essentially playing a part:
The regular intake of carotene products results in carotene being stored in the subcutaneous fatty tissue, and the skin gradually turns orange to yellow-brown.
Coloring can also be accomplished by the route of a chemical change in the horny layer of the skin using what are known as self-tanning preparations. The principal active substance is dihydroxyacetone (DHA). The skin tanning achieved in this way cannot be removed by washing and comes off only with the normal flaking of the skin, after about 10-15 days. Dihydroxyacetone can be referred to as ketotriose and, as a reducing sugar, reacts with the amino acids of the skin and with the free amino and imino groups of keratin via a series of intermediate stages, in a Maillard reaction, to form brown-colored substances, referred to as melanoids, which are occasionally also called melanoidins.
A particular disadvantage of tanning with dihydroxyacetone is that, unlike “sun-tanned” skin, the skin tanned with DHA is not protected from sunburn.
A further disadvantage of dihydroxyacetone is that, particularly under the effect of ultraviolet radiation, it gives off formaldehyde, albeit in amounts which are usually small. There was therefore an urgent need to demonstrate ways in which the decomposition of dihydroxyacetone can be effectively countered.
In a further preferred embodiment the present invention relates to cosmetic and dermatological preparations for the prophylaxis and treatment of cosmetic or dermatological skin changes, such as, for example, unwanted pigmentation, examples being local instances of hyperpigmentation and abnormal pigmentation, such as liver spots, freckles, for example, the inhibition of natural pigmentation, or else for the purely cosmetic lightening of relatively large areas of skin which are quite appropriately pigmented for the individual skin type.
Problems with hyperpigmentation of the skin have a wide variety of causes and are phenomena which accompany numerous biological processes, such as UV radiation, for example, e.g., freckles, ephelides, genetic disposition, abnormal pigmentation of the skin in wound healing or scarring, or skin aging, e.g., age spots, lentigines seniles. Age spots and irregular pigmentation of the human skin are the consequence in particular—according to the current state of knowledge—of continual solar UV irradiation and occur to an increased extent, as the name age spot suggests, with age. With age spots there is generally a local increase in the number of pigment-producing cells, the melanocytes, roughly a doubling of the number of melanocytes in comparison with the skin surrounding the age spots. As a result there is also increased pigmentation: the amount of melanin (pigment) increases in the area of the age spots.
Active substances and preparations which counteract skin pigmentation are known. In practice, use is made essentially of products based on hydroquinone, although on the one hand these products only exhibit their effect after a number of weeks of application and, on the other hand, their application for an excessively long time is objectionable on toxicological grounds. The inhibition of tyrosinase with substances such as kojic acid, ascorbic acid and azelaic acid and also derivatives thereof is also common, but has cosmetic and dermatological drawbacks.
Remedying these deficiencies would also be desirable.
In cosmetology, as well as skin health and skin care, hair care is another area of extremely intensive research.
Hair is the thread-like skin appendage which consists of keratin and is almost universal, though absent from the palms of the hand, soles of the feet, extensor sides of the distal phalanges of the toes and fingers; it is differentiated as long hair (head hair, beard hair, axilla hair, pubic hair—capilli, barba, hirci and pubes, respectively; in men also chest hair), short hair, bristle hair (supercilia, cilia, vibrissae, tragi) and down (lanugo, velus hair). The structure of all of these types of hair is similar on the whole: centrally there is the hair medulla (comprising epithelial cells with eosinophilic horny substance granules=trichohyalin granules), surrounded by the hair cortex (comprising keratinized cells; contains pigments) and the outer skin of the hair (cuticular pili; anuclear epidermis layer) and also by layers of the epithelial and connective-tissue hair sheath.
The hair is divided into the hair shaft, protruding from the skin, and the inclined hair root, reaching into the subcutis, whose layers correspond approximately to those of the epidermis. The thickened lower root end, the hair bulb, sits on a vascular pin of connective tissue, the hair papilla, protruding into it (both as hair base). The bulb in the starting phase (=anagen phase) of hair formation, which is repeated cyclically, is coated in the manner of an onion as a result of continual formation of new cells by its layer near the papilla (matrix), then is later closed, bulblike and entirely keratinized (bulb hair), and finally, in the end phase (=telogen phase), is displaced in the direction of the folicular aperture by a new hair, starting from a newly formed hair papilla.
The substance responsible for individual hair color is melanin. Melanin is formed in the melanocytes, cells which occur in the hair bulb in association with the keratinocytes of the hair medulla. Melanocytes contain melanosomes, as characteristic cell organelles, in which the melanin is formed. The melanin is transferred via the long dendrites of the melanocytes into the keratinocytes of the precortical matrix, and brings about the more or less pronounced blond to brown-black hair color.
Eumelanin is the black-brown pigment. It determines primarily the depth of color of the hair. In brown and black hair it occurs in clearly visible granules.
Pheomelanin is the red pigment, it is responsible for pale blond, blond, and red hair. In terms of its structure, this melanin is very much finer and smaller. The various fractions of the types of melanin give rise to the different colors of hair:                blond hair contains a small amount of eumelanin and a large amount of pheomelanin,        dark hair contains a large amount of eumelanin and a small amount of pheomelanin,        red hair likewise has little eumelanin and a great amount of pheomelanin,        all shades of hair in between result from different proportions in which the two types of melanin are mixed.        
The process of pigment formation can only proceed if sufficient tyrosinase is available. This enzyme is formed more infrequently with increasing age. This then results, gradually, in gray hair. The reason is as follows: with little tyrosinase, less and less tyrosine as well is formed. Hence the production of melanin also goes down. The absent melanin is replaced by the inclusion of air bubbles. The hair appears gray.
This process is generally insidious. It begins at the temples and then extends to the entire head hair system. Subsequently it affects the beard and the eyebrows. Finally, all of the hair on the body is gray.
Gray hair is referred to medically as canities. There are various possibilities for graying. Premature graying, from age 20, is also known as canities praecox.
Canities symptomatica, or symptomatic graying of the hair, can have a variety of causes. These include:                pernicious anemia (vitamin B deficiency anemia),        severe endocrinological disorders, e.g., in the case of thyroid diseases,        acute febrile illnesses,        drug side-effects        cosmetics,        metals.        
The coloring of hair, in particular of living human hair, using natural dyes, has been known since antiquity, particularly for the dye henna, and which for some years has been pushed into the background in favor of synthetic dyes, has for some years been the object of a new interest. The red shade which arises as a result of henna is a disadvantage.
Melanin production, which causes the hair color, decreases with increasing age: the hair becomes gray or white. For some consumers it is a cosmetic desire to reverse or slow down this process. For this purpose, the cosmetics industry in some countries uses lead acetate, which is toxic and therefore prohibited in the European Cosmetics Directive. This lead acetate is applied preferably in the form of a solution to the hair, where it remains for a prolonged period without being washed off.
For the dyeing of keratin-containing fibers, e.g. hair, wool or furs, use is made generally either of direct dyes or of oxidation dyes, which are formed by oxidative coupling of one or more developer components with one another or with one or more coupler components. Coupler and developer components are also referred to as oxidation dye precursors.
Developer components used are usually primary aromatic amines with a further free or substituted hydroxyl or amino group in the para or ortho position, diaminopyridine derivatives, heterocyclic hydrazones, 4-aminopyrazolone derivatives, and 2,4,5,6-tetra-aminopyrimidine and its derivatives.
Specific representatives are, for example p-phenylenediamine, p-tolylenediamine, 2,4,5,6-tetraminopyrimidine, p-aminophenol, N,N-bis(2-hydroxyethyl)-p-phenylenediamine, 2-(2,5-diaminophenyl)ethanol, 2-(2,5-diaminophenoxy)ethanol, 1-phenyl-3-carboxyamido-4-aminopyrazol-5-one, 4-amino-3-methylphenol, 2-aminomethyl-4-aminophenol, 2-hydroxymethyl-4-aminophenol, 2-hydroxy-4,5,6-triaminopyrimidine, 2,4-dihydroxy-5,6-diaminopyrimidine, and 2,5,6-triamino-4-hydroxypyrimidine.
Coupler components used are generally m-phenylenediamine derivatives, naphthols, resorcinol and resorcinol derivatives, pyrazolones, and m-aminophenols. Particularly suitable coupler substances include α-naphthol, 1,5-, 2,7- and 1,7-dihydroxynaphthalene, 5-amino-2-methylphenol, m-aminophenol, resorcinol, resorcinol monomethyl ether, m-phenylenediamine, 2,4-diaminophenoxyethanol, 1-phenyl-3-methylpyrazol-5-one, 2,4-dichloro-3-aminophenol, 1,3-bis(2,4-diaminophenoxy)propane, 2-chlororesorcinol, 4-chlororesorcinol, 2-chloro-6-methyl-3-aminophenol, 2-methylresorcinol, and 5-methylresorcinol.
With regard to further customary dye components, reference is made expressly to the series “Dermatology”, published by Ch. Culnan, H. Maibach, Verlag Marcel Dekker Inc., New York, Basle, 1986, vol. 7, Ch. Zviak, The Science of Hair Care, chap. 7, pages 248-250 (direct dyes) and chap. 8, pages 264-267 (oxidation dyes), and also the “European Inventory of Cosmetics Raw Materials”, 1996, published by the European Commission, available in disk form from the Bundesverband der deutschen Industrieiund Handelsunternehmen für Arzneimittel, Reformwaren und Köperpflegemittel e.V., Mannheim.
Although intense colorations with good fastness properties can be achieved with oxidation dyes, the development of the color takes place generally under the influence of oxidizing agents such as H2O2, for example, which in certain cases can result in damage to the fiber. Furthermore, certain oxidation dye precursors or particular mixtures of oxidation dye precursors may occasionally have a sensitizing effect in people with sensitive skin. Direct dyes are applied under relatively gentle conditions, but their disadvantage is that the colorations frequently have only inadequate fastness properties.
It would be desirable to improve the independent production of melanin by the hair, but without resort to coloring agents and, in particular, oxidizing agents such as H2O2, for example. Furthermore, the compositions should have very little sensitization potential, if any at all.
The Elias skin model, which is currently recognized in the art (P. M. Elias, Structure and Function of the Stratum Corneum Permeability Barrier, Drug Dev. Res. 13, 1988, 97-105) describes the horny layer as a two-component system, similar to a brick wall (bricks and mortar model). In this model the horny cells (corneocytes) correspond to the bricks, and the lipid membrane in the intercellular spaces, which is of complex composition, corresponds to the mortar. This system is essentially a physical barrier to hydrophilic substances, but, because of its narrow and multilayered structure, can also be passed only with difficulty by lipophilic substances as well. The particular structure of the horny layer on the one hand protects the skin and on the other hand stabilizes its own flexibility by binding a defined amount of water.
Mechanical stresses as well, such as compressive forces, impact forces or shear forces, for example, can be intercepted to a surprising degree by the horny layer on its own or in conjunction with the deeper layers of the skin. Relatively large compressive, torsional or shear forces are transmitted to deeper layers of the skin via the intermeshing of the epidermis with the corium.
The regulation of the water content and moisture content is one of the most important functions of the epidermal lipid membrane. However, it not only has a barrier effect to external chemical and physical influences, but also contributes to the cohesion of the horny layer.
The lipids of the horny layer consist essentially of ceramides, free fatty acids, cholesterol and cholesterol sulfate, and are distributed throughout the horny layer. The composition of these lipids is of decisive importance for the intact function of the epidermal barrier and hence for the impermeability of the skin to water.
Even cleansing of the skin with a simple water bath—without the addition of surfactants—initially causes the horny layer of the skin to swell. The degree of this swelling depends, among other factors, on the duration of the bath and its temperature. At the same time, water-soluble substances are washed off or out, such as water-soluble dirt constituents, for example, but also substances endogenous to the skin which are responsible for the water-binding capacity of the horny layer. In addition, as a result of surface-active substances which are endogenous to the skin, skin fats are also dissolved and washed out to a certain extent. After initial swelling, this causes the skin subsequently to dry out, a process which may be further substantially intensified by detersive additives.
In healthy skin, these processes are generally of no consequence, since the protective mechanisms of the skin are easily able to compensate for such slight disturbances to the upper skin layers. However, even in the case of non-pathological deviations from the normal state, as a result, for example, of environmentally induced wear damage or irritation, photodamage, aging skin, and so on, the protective mechanism at the skin's surface is impaired.
In the case of aged skin, for example, regenerative renewal takes place at a slower rate, and the water-binding capacity of the horny layer, in particular, suffers a decrease. The skin therefore becomes inflexible, dry, and chapped (“physiologically” dry skin). Barrier damage is the result. The skin becomes susceptible to adverse environmental influences such as the invasion of microorganisms, toxins, and allergens. As a consequence, toxic or allergic skin reactions may even occur.
In the case of pathologically dry and sensitive skin, barrier damage is present a priori. Epidermal intercellular lipids become defective or are formed in inadequate amounts or compositions. The consequence is an increased permeability of the horny layer and inadequate protection of the skin against loss of hygroscopic substances and water.
The barrier effect of the skin can be quantified via the determination of the transepidermal water loss (TEWL). This is the evaporation of water from inside the body, without taking account the loss of water during perspiration. Determining the TEWL value has proven extraordinarily informative and can be used to diagnose chapped or cracked skin, to determine the compatibility of surfactants with different kinds of chemical compositions, and more besides.
For the beauty and well-cared-for appearance of the skin, the proportion of water in the topmost layer of the skin is of the utmost importance. Within a limited extent it can be favorably influenced by the introduction of moisture regulators.
Anionic surfactants, which are generally constituents of cleansing preparations, are able lastingly to increase the pH in the horny layer, which severely hinders regenerative processes that serve to restore and renew the barrier function of the skin. In this case, a new, frequently very adverse state of equilibrium is established in the horny layer between regeneration and the loss of essential substances as a result of regular extraction; this equilibrium state has a decisive adverse effect on the external appearance of the skin and on the physiological functioning of the horny layer.
Cosmetic skin care means primarily that the natural function of the skin as a barrier against environmental influences, e.g., dirt, chemicals, microorganisms, and against the loss of substances endogenous to the body, e.g., water, natural fats, electrolytes, is strengthened or restored.
If this function is disrupted, there may be increased absorption of toxic or allergenic substances or infestation by microorganisms and, as a consequence, toxic or allergic skin reactions.
A further aim of skin care is to compensate the loss of fat and water as a result of daily washing. This is particularly important if the natural regeneration capacity is insufficient. Moreover, skin care products ought to protect against environmental effects, especially against sun and wind, and ought to delay skin aging.
Chronological skin aging is caused, for example, by endogenous, genetically determined factors. As a result of aging, within the epidermis and dermis, the following structural damage and functional disorders, for example, occur, which may also come under the term “senile xerosis”:    a) dryness, roughness, and formation of dryness wrinkles    b) itching, and    c reduced fat restoration by sebaceous glands, e.g., after washing.
Exogenous factors, such as UV light and chemical noxae, may have a cumulative effect. Within the epidermis and dermis, in particular as a result of exogenous factors, the following structural damage and functional disorders, for example, occur in the skin:    d) increased susceptibility to mechanical stress, e.g., chapping.
Products for the care of sensitive, itchy and/or dry skin or products for the treatment of or prophylaxis of DNS damage are known per se. Their efficacy, though, is limited.
The present invention relates in particular also to cosmetic preparations that provide additional, effective protection against damaging oxidation processes in the skin, but also for the additional protection of cosmetic preparations themselves and/or for the additional protection of the constituents of cosmetic preparations against harmful oxidation processes.
It would be advantageous to be able to provide cosmetic and dermatological preparations based on a gel matrix, in particular including suitable active substances, which counter the above-described unwanted skin phenomena such as                the dryness, roughness, chapping and reduced fat restoration of the skin,        the after-effects of exogenous exposures such as UV light and shaving, especially sunburn and shaving burn,        other irritant and inflammatory skin reactions, including itchy skin,        hair growth as a cosmetic desire, such as in the case of woman's beard, for example,        aging skin phenomena such as lack of elasticity, increasing wrinkliness and age spots and to strengthen the physiology of the skin with regard to        the barrier properties,        the maintenance of skin homeostasis,        the growth of the hair as a cosmetic desire and also to enable a cosmetically desired        modulation of the pigmentation of skin and hair.        
With topical application of the cosmetic or dermatological preparations of the invention, comprising an effective amount of active substances used, it is surprisingly possible to achieve effective treatment, but also prophylaxis, in the case of                reduced skin hydration or reduced moisture content of the skin        aging skin wrinkles        photo-aged skin        greasy and unclean skin        reduced skin elasticity        age spots and other abnormal pigmentations of the skin, e.g., melasma,        after-reactions of the skin to UV light (sunburn)        after-reactions of the skin to shaving (shaving burn)        dysfunction of metabolic homeostasis of the skin        reduced cell-cell communication        reduced DNA synthesis and/or reduced DNA repair        activation of metalloproteinases and/or proteases        activation of cyclooxygenases and lipoxygenases of the skin        alterations to normal hyaluronic acid and glucosaminoglycan homeostasis        deviations from the normal post-translational modifications of connective-tissue proteins, glycosaminoglycans and other structural constituents        disruptions to the ceramide, lipid and energy metabolism of the skin        disruptions to melanin metabolism and the melanosoma processing of the skin        deficient, sensitive or hypoactive skin conditions or deficient, sensitive or hypoactive conditions of skin appendages        changes in transepidermal water loss        changes in the amount of natural moisturizing factor        changes in normal lipid peroxidation        inflammatory phenomena and/or itching        formation of flakes in the hair region        reduced and also unwanted hair growth        disruptions to the barrier function.        
Additionally it has been found that when a preparation according to the invention is employed it may be possible to increase the general sensation of freshness of the skin.
The mechanism of action of patches or cosmetic matrices for administering cosmetic substances into and onto the skin is subject to a functional principle similar to that of transdermal therapeutic systems (TTS). The terms patches, cosmetic/dermatological matrices and cosmetic/dermatological pads are sometimes used synonymously below.
Transdermal therapeutic systems for delivering active substances into and/or through the skin have been known for a long time and constitute patch-like systems which in particular are doped with drugs.
The topical administration of active cosmetic and dermatological substances via patch systems or cosmetic matrices offers two main advantages:                First, this administration form produces first-order release kinetics of the active substance, thereby allowing a constant level of active substance to be maintained in the skin over a very long period of time.        Secondly, an additional intensive care of the skin can be brought about via appropriate systems.        
The time-dependent release of the active cosmetic substance from a TTS takes place in dependence on its TTS/skin partition coefficient and its diffusion in the region of the TTS and of the skin.
Both factors are determined by the composition of the matrix, thereby allowing the amount released per unit time and the duration of activity to be influenced directly. Normally hydrocolloids, solubilizers and enhancers are used for this purpose, allowing improved solubility and diffusion and also a more rapid passage of the substance from TTS into the skin.
Ideally, first-order release kinetics are achieved, allowing the release of equal quantities per unit time.
One embodiment of such transdermal systems which has been well described in the technical literature is that of matrix systems or monolithic systems in which the active cosmetic substance is incorporated directly into the pressure-sensitive adhesive. In the ready-to-apply product a pressure-sensitive adhesive matrix of this kind, comprising active substance, is equipped on one side with a backing, which is occlusive for the active substance, while on the opposite side there is a backing film equipped with a release layer, which is removed prior to application to the skin (kleben&dichten, No. 42, 1992, pp. 26 to 30).
The aforementioned properties of a TTS avoid the need for frequently repeated administration and avoid burdening the skin with high concentrations of active substances, and so reduce irritation to the skin, which is unavoidable in the event of repeated administration of liquid and semisolid administration forms.
In summary, the advantages of the TTS lie in a distinctly improved compliance on the part of users, which is attributable to the simple and rapid administration and to the long-lasting efficacy of transdermal therapeutic systems.
One basic requirement of a TTS is effective adhesion to skin, which must be maintained over the entire period of the intended dosing of active substance, and another is the ability for the TTS to be removed without residue. Painful redetachment of the active substance patch after a prolonged period of wear is a frequent observation. As well as adhesives which are coated in solution onto the backing, the adhesives used also include solvent-free systems, such as hot-melt adhesives. A feature of these adhesives is that in the course of their coating it is possible to forego the use of organic solvent and dispersion medium. Hot-melt adhesives are converted to a liquid form by heating and are applied thus as a melt to the respective patch backing. As well as technical aspects, such as solvent processing, plant design with anti-explosion measures, and environmental protection strictures, medical reasons as well play a part in the choice of solvent-free adhesives. Transdermal therapeutic systems are generally applied to healthy, intact skin.
Self-adhesive matrix systems for administering active cosmetic substances are among traditional applications in Asia, particularly in Japan, and are defined in the Japanese pharmacopoeia under the terms “cataplasm”. Cataplasms, accordingly, are commonly prepared by mixing glycerin, water or other suitable liquids with finely pulverized active substances, with the addition of essential oils.
Glycerin functions here as a humectant, in order to prevent the cataplasms from drying out prematurely in use.
Whereas in the traditional Asian preparations natural thickeners such as alumina, etc., are employed, recent decades have seen the use, more and more, of modern synthetic raw materials, such as polyacrylic acid as a gel former, for example, for their production. This allows the cataplasms, which are commonly pasty, to be produced as hydrogel matrices having improved attractiveness and user-friendliness.
EP 1 136 057 describes an aqueous gel system for cosmetic use without backing or liner, with a light transmittance of min. 70%.
EP 0 507 160 describes cataplasms containing lidocaine.
A disadvantage of the cataplasms described is that the production of the base matrices requires many different individual components such as gel formers, thickeners, plasticizers, humectants, stabilizers, emulsifiers, pH regulators, antioxidants, etc., and possibly also solubilizers and penetration enhancers in the case of active substance cataplasms. Since the adhesive performance and consistency of such a matrix is a function of the interaction of all of the individual components, targeted product development/optimization with regard to these fundamental product requirements is, correspondingly, time-consuming and arduous.
The production of polymer matrices, especially gel matrices, from polyacrylates has likewise been known for many years and is described for example in EP 0 507 160, JP 11-228340 and JP 04178323. Gel matrices are used, among other things, as an adhesive base and as an active substance reservoir in transdermal systems. Such systems have an adequate bond strength, especially to moist skin (buccal patches), but because of inadequate cohesiveness cannot be removed again completely when required.
In order to form a gel with a defined structure it is necessary for polyacrylic acid to be cross-linked. The nature of the cross-linker makes a critical contribution to the structure of the resultant gel. The customary cross-linking agents may be metal ions (e.g.: Al3+ ions), or organic compounds. Cross-linking with aluminum salts proceeds via the coordination of the oxygen functions of the polyacrylic acid to the Al3+ ions. A very close-meshed gel with high viscosity is formed, the viscosity of the gel being controllable only via the amount of cross-linker (Handbook of Pressure Sensitive Technology, page 458 ff, 1999).
JP 11-228340 discloses polyacrylic acid-based gels which utilize Al+3 compounds as cross-linkers. The use of the mandatory aluminum compound as a cross-linking agent is limited, since otherwise the physical properties of the gel are impaired. If the proportion of aluminum cross-linker is too high the gel becomes too hard.
Known from the literature are further examples of cross-linking with polyvalent metal ions, e.g., U.S. Pat. No. 3,900,610 (zinc salts), U.S. Pat. No. 3,770,780 or U.S. Pat. No. 3,790,533 (titanium compounds). Ionic cross-linking with metal ions leads to hard, viscous polymer gels with low tack (Handbook of Pressure Sensitive Adhesive Technology, page 458 ff, 1999).
EP 303445 discloses a patch with a monolithic gel matrix based on water-soluble polymers. Mandatory constituents are clebopride or a pharmaceutically acceptable salt thereof as active substance, water, water absorbers, and water-soluble polymers. As water-soluble polymers the skilled worker is able to select from a range of known polymers such as polyvinyl alcohol, gelatin, polyacrylic acid, sodium polyacrylates, methylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, rubber and other cross-linkable polymers and also mixtures thereof.
EP 976382 describes a patch comprising a matrix composed of a system which is hydrophilically gelling in aqueous phase and which is formed from gelan gum and at least one further hydrocolloid. Gelan gum is claimed mandatorily. Gelan gum is understood by the skilled worker, as defined by technical dictionaries, to comprise hydrocolloids obtained from the following marine plants: Agardhiella tenera, Furcellaria fastigiata, Hypnea cervicornis, musciformis, spicifera, Suhria vitata. The term does not comprise sea algae extracts. Nor is there any mention of the essential aspects of self-adhesive properties, the adjustability of bond strength and elasticity of the resultant matrices.
A further problem associated with the cross-linking of polyacrylic acid to form a self-adhesive matrix or gel is that a matrix once produced, having defined physical properties, viscosity, tack, etc., must have the same defined properties in a later production operation. This reproducibility is difficult if not impossible to realize with the cross-linking technologies that are presently known.
A further problem apparent in connection with cosmetic skin treatment is that unwanted skin phenomena cannot be given optimum treatment by the topical application of active substances in the form of emulsion formulations and the like. Particularly in the case of skin phenomena which are relatively difficult to treat, such as wrinkles, loss of skin elasticity, and age spots, and also irritative skin phenomena such as sunburn and shaving burn, etc., there is a lack of a cosmetic application system which offers intensive provision of the active substance in conjunction with beneficial effects on the skin in order to influence the skin condition positively.
It would therefore be desirable to develop a simple polymer matrix system for cataplasms/hydrogels which, with a few ingredients, allows matrices of defined consistency and bond strength to be produced in a controlled fashion.
It would further be advantageous to have available a polymer matrix in which water-soluble or hydrophobic active substances can be incorporated and can be delivered to the skin in a controlled fashion.
It would further be desirable to be able to provide patches or cosmetic matrices which comprise aforementioned polymer matrices and can be used as TTS, pads or patches.
It would further be desirable to be able to provide a gel matrix suitable as a cosmetic application form for the treatment and also for the prophylaxis of unwanted skin phenomena, and to remedy the disadvantages of the prior art. In this context the aim in particular is to take into account the skin care and moisturizing aspect.